The present invention relates to actuators and deals more particularly with linear displacement actuators.
Motors and actuators for controllers of windows and other components on motor vehicles require many rotating components involving reduction gearing in order to bring about an essentially or partially linear displacement of some other component such as a side window, a sunroof, part of a locking system, a light source, a door, or some other closure member.
Such devices entail a great many parts, are bulky, expensive and require a relatively large amount of energy because of the numerous areas of friction between the various parts.
Hence, there is a need for an improved linear displacement actuator.
The present invention relates generally to a linear displacement actuator which involves the use of a minimum number of parts.
The subject of the invention is a linear displacement actuator which includes a male part and a female part. One part includes a screw thread and the other part includes at least one peripheral rib which collaborates with the screw thread. The inside diameter of the female part, increased by the depth of the screw thread, is greater than the outside diameter of the male part. The female part bears linear actuators arranged at right angles in a support and is free to be displaced axially with respect to the male part. The linear actuators place the female part in sinusoidal vibration in two perpendicular directions with an appropriate phase shift between the vibrations, and displaces, rotation-wise, the line of contact between the screw thread and the at least one peripheral rib. The screw thread and the peripheral rib remain motionless in terms of rotation and therefore bring about relative linear displacement of the female part and of the male part.
In another embodiment of the invention, the male part is a shaft having an external screw thread and the female part comprises internal circular ribs and grooves.
In yet another embodiment, the male part is a shaft with an external screw thread and the female part is a nut with an internal tapped thread of the same pitch as the external screw thread of the shaft but with a different thread slope.
In yet another embodiment, the female part is placed in a cage-like support which is free in terms of axial displacement along the shaft, between the linear actuators and corresponding return springs, each return spring being diametrically opposite a linear actuator.
Finally, in yet another embodiment, the linear actuators are piezoelectric or magnetostrictive actuators, or are electromagnetic elements powered from a suitable energy source.